EnforceEntireTree.cs

public class EnforceEntireTree
{
    public void Process(LoggedInArgs args)
    {
        User user = User.FromName(args.Username, true);
        Assert.IsNotNull(user, "user");

        string key = "/" + user.Name + "/UserOptions.View.ShowEntireTree";
        user.Profile.Initialize(user.Name, true);
        user.Profile[key] = "true";
        user.Profile.Save();

         // Get the shell site here
        var site = Sitecore.Sites.SiteContext.GetSite("shell");
        RegistryCache registryCache = CacheManager.GetRegistryCache(site );
        registryCache.Clear();
    }
}